This invention relates to a cruise control apparatus for an automotive vehicle. A cruise control apparatus is a device that enables the driver of a vehicle to select a desired target speed for the vehicle and then controls the output of the engine of the vehicle so as to maintain the selected target speed without the driver having to depress the accelerator pedal. A typical cruise control apparatus controls the engine output by varying the opening of the throttle valve of the engine.
Conventional cruise control apparatuses are able to perform fairly good control of vehicle speed when the vehicle is travelling on a level road. However, when the vehicle is travelling on a road which is not level, and particularly on one with a succession of upwards and downwards slopes, with a conventional cruise control apparatus, the deviation of the vehicle speed from the target speed becomes large, hunting of the engine frequently occurs, and the ride becomes uncomfortable for the passengers of the vehicle.